1. Technical Field
The invention relates generally to integrated circuit design, and more particularly, to migrating an integrated circuit (IC) layout for, for example, alternating aperture phase shift masks (AltPSM) or gridded layouts.
2. Background Art
Integrated circuit (IC) chip layouts or designs are created in a graphical computer programming language, and stored in a computer storage medium (such as a disk, tape, physical hard drive, or virtual hard drive such as in a storage access network). If the designer does not fabricate chips or the photolithographic masks used to fabricate chips, the designer transmits the resulting design by physical means (e.g., by providing a copy of the storage medium storing the design) or electronically (e.g., through the Internet) to such entities, directly or indirectly. The stored design is then converted into the appropriate format (e.g., GDSII or Oasis) for the fabrication of photolithographic masks, which typically include multiple copies of the chip design in question that are to be formed on a wafer. The photolithographic masks are utilized to define areas of the wafer (and/or the layers thereon) to be etched or otherwise processed.
Alternating aperture phase shift masks (AltPSM) are used extensively to print sub-wavelength features. The use of AltPSM in manufacturing creates topology restrictions in the design. AltPSM has been used primarily for printing the gate layer of chips, and may be required in future generations for routing layers. Gridded layouts have shapes on certain layers that are drawn predominantly or exclusively in one direction (i.e. a set of parallel lines of differing lengths). Migration of designs from one technology (size) generation to the next is increasingly important in order to minimize the cost in resources and time needed to get the next generation design to market. Unfortunately, no adequate techniques exist to migrate routing from general topologies to AltPSM restricted topologies.